Segmented externally finned tubes employed in heat exchangers have proved to be quite successful as regards other types of finned heat exchanger tubes. The segmented fins appear as radially outwardly extending spines located about the periphery of the tube and along the length thereof. Because of the segmentation of the fins, a high degree of turbulence in the fluid, typically air, passing across such fins is generated; and such turbulence in segmented fins is much greater than that in heat exchangers using otherwise identical, smooth finned tubes. Because, in externally finned heat exchanger tubes, the overall heat transfer coefficient is largely controlled by the air or fluid side heat transfer coefficient, the greater degree of turbulence found in segmented fin structure provides for greater heat transfer because of an enhanced heat transfer coefficient.
In the usual case, segmented fins are applied to a tube by helically winding a tape formed of heat conductive material about the tube to be in heat transfer relation thereof. One edge of the tape is generally transversely slit while the other edge is continuous. The slit edge is bent at approximately right angles to the unslit edge before or during the winding process with the result that the slits delineate the spines which fan out and extend generally radially outwardly through an arc length of 360.degree. about the tube.
In commonly assigned copending applications of David T. Hill, Ser. No. 06/641,476 filed Aug. 16, 1984, and Robert P. Failing, Ser. No. 06/641,474 filed Aug. 16, 1984, and entitled "Segmented Fin Heat Exchanger Core" and "Heat Exchanger Core and Heat Exchanger Employing the Same", respectively, the details of which are herein incorporated by reference, there are disclosed improvements in prior art segmented externally finned heat exchanger cores. As more fully stated in those applications, by providing one or more spine free areas on the tubes, i.e., by eliminating the spines forming parts of the segmented fin in various areas of the tube, heat exchange capability very nearly equal to that obtainable with prior art structures having spines throughout a 360.degree. arc length is obtainable while at the same time several advantages over such prior art constructions are obtained. For example, the elimination of the spines in certain areas cuts almost by 50% the amount of material required in forming the spines with but negligible loss in heat transfer capability. Moreover, heat exchanger arrays employing tubes having spine free areas may be more compactly arranged providing for size advantages. Finally, the elimination of the spines in some areas on the tubes somewhat lowers the so-called "air side pressure drop" across a heat exchanger core such that less energy is required to maintain the desired air flow across the heat exchanger core.
This invention is directed to a method of forming segmented externally finned heat exchanger tube having spine free areas of the types disclosed in those copending applications in a most economical fashion.